This invention relates in general to a seamless tiled display and, in particular, to seamless tiled active liquid crystal display (LCD).
Tiled displays have been used frequently in super-large-screen displays for indoor and outdoor applications to display character and full-color image, such as sports stadiums, exhibition halls etc. Several types of tiled full color super-large-screen displays have been used or proposed. One type known as tiled flat CRT, such as Jumbotron, is a kind of flat matrix CRT which has a hot filament cathode, mesh grid and anode. The anode voltage is about 8 kv, and one display tile includes about 20 color pixels. This kind of display has a good color quality image, but a short lifetime and a high anode voltage.
Another conventional tiled display system currently used is known as a light emitting diode (LED) tiled display. One pixel includes several red, green and blue (R, G, B) LED lamps or chips. It can display a good quality full color image and high brightness, and can be used in both indoor or outdoor applications. But this kind of tiled display is very expensive especially for a super-large-screen display, because it must employ a large number of small individual LEDs that have diameters of about 5 mm.
Another conventional tiled display system is a tiled liquid crystal display (LCD) as described in U.S. Pat. No. 5,557,436. In this kind of display, a passive LCD and a hot cathode fluorescent lamp (HCFL) back-light are used. The color quality, contrast and brightness are not quite satisfactory. Therefore, at present, this kind of display is only used for displaying characters. On the other hand, the seam width of this tiled display is normally quite large. This is caused by the use of a wide sealing wall, a thick front plate and thick back plate. This kind of display cannot be used for a high resolution tiled display.
This invention is based on active LCD and backlight to make a seamless tiled display. The problems described above with conventional tiled displays are alleviated or avoided altogether.
This invention reduces the visually apparent seam width of the tiled display. For this purpose, a thin glass or plastic front plate of LCD is used. The thickness of the front plate is preferably in the range of about 0.02 to 0.7 mm.
To reduce the visually apparent seam width of the tiled display, a reflective layer is employed on the side wall of the back plate to reflect the light emitted from the backlight. Therefore, the apparent seam width can be reduced.
As explained above, conventional LCD devices employ thick front and back plates because of the requirement that the device be mechanically sturdy. By using a back light or reflector with adequate mechanical strength and connecting LCD tiles to the back light or reflector to lend mechanical strength to the tiles, it is possible to use thin front and back plates in the LCD tiles, thereby reducing or eliminating apparent seam widths and so that the tiled display appears to be seamless.
A plastic LCD device may be conveniently made by aligning LC cells between two sheets of plastic and using a laser to cut the two sheets into smaller pieces by melting the plastic in the two sheets along the lines that are cut. The melting of the plastic at the edges of the smaller pieces causes the front and back portions of the pieces to bond and form a sealing wall. Where a sturdier sealing wall is desired, an adhesive material may be applied between the two sheets along the lines of cutting by the laser to bond the two sheets prior to the cutting process. Therefore, the heat of the laser will melt the plastic material of the two sheets as well as the adhesive material to form a sturdy sealing wall for the LCD devices formed.
To further enhance the mechanical strength of the plastic LCD""s, rivets may be formed connecting the front and back plastic plates by applying a drilling laser to the device. The laser may be applied to form one or more holes in the device by melting the front and back sheets at selected spots and the melted plastic of the two sheets are bonded together to form a rivet. Alternatively, for high resolution displays, the rivets are formed without forming visible holes.